Apparatus for plugging well bores with hardenable fluent substances

ABSTRACT

As a preferred embodiment of the apparatus of the present invention disclosed herein, an expansible bag mounted around a first tubular body is operatively arranged to be expanded into engagement with a well bore wall by a hardenable fluent substance initially contained in a selectively-operable displacement assembly including a second tubular body suspended from a cable and releasably coupled to the first body. Biasing means are operatively arranged for imposing opposed axial forces against the ends of the expanded bag to securely anchor the tool until the fluent substance has solidified. The new and improved apparatus further includes a unique release mechanism which is capable of withstanding severe shocks and other forces which may be imposed on the apparatus to guard against the unexpected or premature uncoupling of the two tubular bodies as it is being moved into a well bore and operated. The release mechanism is, however, easily and positively released by the discharge of the fluent substance from the displacement assembly.

United States Patent 1191 Urbanosky Jan. 8, 1974 APPARATUS FOR PLUGGINGWELL Primary Examiner.1ames A. Leppink BORES WITH HARDENABLE FLUENTAttorney-Ernest R. Archambeau, Jr. et a1.

' SUBSTANCES [5 7] ABSTRACT As a preferred embodiment of the apparatusof the Inventor: Harold J. Urbanosky, Pearland,

Tex.

[73] Assigneez schlumberger Technology present invention disclosedherein, an expans ible bag Corporation, New York mounted around a firsttubular body 1s operatlvely arranged to be expanded into engagement witha well Filed; 1"- 1 1972 bore wall by a hardenable fluent substanceinitially [211 App]. 245,421 contained in a selectively-operabledisplacement assembly including a second tubular body suspended from acable and releasably coupled to the first body. [52] US. Cl. 166/181,166/187 Biasing means are operatively arranged f imposing [51] Int. ClE21b 33/127 Opposed axial forces against the ends f the expanded ofSearch bag to ecurely anchor the too] the fluent sub- 166/206, 214stance has solidified. The new and improved apparatus further includes aunique release mechanism which is References Cited capable ofwithstanding se'vere shocks and other UNITED STATES PATENTS forces whichmay be imposed on the apparatus to 2,815,817 12/1957 Conrad 166/181guard against the unexpected of premature uncou- 2,ss5,oo7 5 1959 Hoffer166/181 P g the two tubular bodies as it is being moved 1,681,596 8/1928Reichard 166/181 into a well bore and operated. The release mechanism2,885,011 5/1959 Frost 166/181 is, however, easily and positivelyreleased by the dis- Anderson 611 3i. charge of the fluent ubstance fromthe displacement 2,726,848 12/1955 Montgomery et a1. assembly 3,429,5952/1969 McGill 285/320 17 Claims, 7 Drawing Figures PATENTED 81974 3. 783940 sum 1 or 3 F/Gl PATENTED 4 SHEET 3 (If 3 APPARATUS FOR PLUGGING WELLBORIES WITH HARDENABLE FLUENT SUBSTANCES In various well-completionoperations it is often desired to place a fluid-tight barrier or plug ata desired location in a larger-diameter well casing below the lower endof a substantially-smaller well pipe or tubing string. Typically,so-called through-tubing bridge plugs such as those shown in U.S. Pat.No. 3,556,215, U.S. Pat. No. 3,578,079 and U.S. Pat. No. 3,578,083 aswell as the patents mentioned-therein are employed for situations ofthis nature. As illustrated in those patents, these tools generallyinclude a fluid-displacement device in an upper housing which issupported by a suspension cable and releasably-coupled to a dependingbody carrying an initially-collapsed expansible tubular bag. Once thetool has been lowered through the tubing string and is in the well borebelow its lower end, the displacement device is operated to discharge ahardenable plastic or cementitious composition into the expansible bagso as to firmly expand the bag into sealing contact with the well borewalls. After the remainder of the hardenable substance has beendeposited on top of the bag, the upper portion is uncoupled from thelower portion of the tool and returned to the surface. Thereafter, oncethe hardenable substance within and on top of the expanded bag hashardened, a fluidbypass passage through the lower portion of the tool isclosed to prevent fluid or pressure communication between the well boreintervals above and below this barrier.

Although these well-completion tools have met with considerablecommercial success, the problem of releasably coupling the upper andlower portions of these tools has not been satisfactorily solvedheretofore. For example, those skilled in the art will appreciated thatany well-completion tool must be capable of withstanding severe impactsand various adverse forces. As a result, any release mechanism employedfor releasably coupling the two portions of these through-tubing bridgeplugs together must be insensitive to sharp shocks and extremeaccelerational forces to prevent the tool from being prematurelyseparated. On the other hand, these release mechanisms must also becapable of being selectively actuated with a minimum effort to becertain that the upper and lower portions of the tool can be separatedfrom one another without moving the lower portion upwardly from theposition where the expanded bag is intended to be placed.

Accordingly, it is an object of the present invention to provide new andimproved well-completion apparatus for plugging a well bore with aninitially-fluent sub stance and including upper and lower bodies whichare releasably coupled together in such a manner that they can bereliably uncoupled only after the fluent substance has been placed inthe well bore and with a minimum of effort.

This and other objects of the present invention are attained byproviding upper I and lower tandemlydisposed bodies having a fluidchamber and a displacement piston adapted to displace a hardenablefluent substance from the chamber onto an extendible support carried onthe lower body. Coupling means releasably intercouple the two bodiestogether and include a laterally-movable abutment on one of the bodiescoengaged with a fixed abutment on the other body, and a latch memberco-operatively arranged to be moved 2 by the piston from a firstposition retaining the abutments co-engaged under extreme shock loadsand cable tension forces to a second position for reliably disengagingthe movable abutment from the fixed abutment with a minimum of effort.

The novel features of the present invention are set forth withparticularity in the appended claims. The invention, together withfurther objects and advantages thereof, may be best understood by way ofthe following description of exemplary apparatus employing theprinciples of the invention as illustrated in the accompanying drawing,in which:

FIG. 1 depicts a preferred embodiment of a wellcompletion tool arrangedin accordance with the principles of the present invention as the toolis being lowered through a tubing string to a desired location in a wellbore;

FIGS. 2A-2C are successive cross-sectional elevational views of the newand improved tool depicted in FIG. 1 illustrating the initial positionsof the various el ements thereof before the tool has been actuated;

FIG. 3 is an enlarged view of a portion of the selectively-operatedcoupling means employed with the present invention; and

FIGS. 4 and 5 successively depict the tool shown in FIG. 1 as it isbeing operated to plug a selected well bore interval and after the uppertool portion has been separated from the lower portion.

Turning now to FIG. 1, a well-completion tool 10 incorporating theprinciples of the present invention and dependently supported by asuspension cable 11 is depicted as it is being lowered through a stringof tubing 12 toward a selected position below the lower end of thetubing string within a larger-diameter well bore 13 which, in thisinstance, is cased as at 14. If desired, a typical casing collar locator15 may be incorporated with the tool 10 for determining the depth atwhich the tool is to be halted.

In the preferred embodiment depicted, the new and improvedwell-completion tool 10 includes selectivelyoperable fluid-displacementmeans 16 arranged in an upper body 17 of the tool and carrying a supplyof an initially-fluent hardenable material which, upon command from thesurface, is displaced into extendible, wall-engaging support means suchas an expansible tubular bag 18 which is carried on an elongated body 19detachably coupled below the upper body and adapted for supporting thefluent substance until it hardens into a solidified mass. As willsubsequently be explained in greater detail, the upper and lower toolbodies 17 and 19 are releasably coupled together by selectively operablecoupling means 26) cooperatively arranged for releasing the lower bodyin response to the operation of the displacement means 16. Biasing means21 carried on the lower body 19 are arranged for selectively imposingopposed axial forces against the ends of the expanded bag 18 to anchorthe tool 10 after the tubular bag has been filled with a sufficientquantity of the fluent substance to expand it outwardly into sealingengagement with the well casing 14. Following the operation of thedisplacement means 16 and the release of the tool bodies 17 and 19, theupper body is returned to the surface by respooling the cable 11.Thereafter, once sufficient time has elapsed for the fluent substance toadequately harden for forming an impermeable transverse bridge or abarrier permanently plugging the well casing 14, time-controlled bypasscontrol means 22 mounted on the lower end of the body 19 operate topermanently close a bypass passage 23 in the lower body which istemporarily left open for equalizing pressure differentials actingacross the inflated bag 18 until the fluent substance supported therebyhas hardened.

Turning now to FIGS. 2A-2C, a cross-sectioned elevational view is shownof the well-completion tool as it appears before the collapsed bag 18carried thereon is expanded. As previously mentioned, the tool 10carries a substantial volume of a hardenable substance 24 which, uponoperation of the fluiddisplacement displacement means 16, is forciblydisplaced into the tubular bag 18 to expand it outwardly into sealingengagement with the well casing 14. Accordingly, the upper body 17 ofthe tool 10 is arranged to provide an enlarged chamber 25 in its upperportion that is joined by an axial passage 26 to an enlargeddiameterlongitudinal bore 27 extending substantially the full length of the bodyand terminating at its lower end. The upper portion of the lower body 19is also enlarged and similarly provided with an enlargeddiameterlongitudinal bore 28 which extends upwardly to the upper end of thebody. The adjacent ends of the upper and lower bodies 17 and 19 arecomplementally fitted together and fluidly sealed as at 29, with the twobodies being releasably coupled to one another by the coupling means 20so that their respective bores 27 and 28 together define a combinedfluid chamber 30 of substantial volumetric capacity.

The fluid-displacement means 16 also include a piston 31 initiallypositioned in the fluid chamber 30 just above the upper surface of thefluent substance 24. In this manner, upon downward movement of thepiston 31, the fluent substance 24 will be displaced from the fluidchamber 30 and into the expansible bag 18. By providing one or morelateral ports 32 in the upper body 17, well bore fluids will be admittedinto the longitudinal bore 27 for maintaining the space above the piston31 as well as the fluent substance 24 in the fluid chamber 30 at thehydrostatic pressure of the well bore fluids.

To move the displacement piston 31 downwardly, the fluid-displacementmeans 16 further include a cylindrical weight 33 initially disposed inthe enlarged bore 27 immediately above the piston and releasablysupported therein by two or more inwardly-movable upright latch fingers34 arranged on the upper end of the weight. As illustrated in FIG. 2A,the latch fingers 34 have outwardly-enlarged heads 35 which are adaptedto be received in an enlarged portion 36 of the axial passage 26immediately above the upper end of the enlargeddiameter longitudinalbore 27 and defining a shoulder 37 to support the heads so long as thefingers are laterally separated. To retain the latch fingers 34initially separated, an actuating piston 38 disposed in the chamber 25carries a depending rod 39 which extends through the axial passage 26into the enlarged recess 36 so as to be interposed between the opposedheads 35 of the fingers so long as the actuating piston is not furtherelevated by a compression spring 40 mounted within the chamber.

To retain the actuating piston 38 in its position depicted in FIG. 2A,the upper portion of the chamber 25 is initially filled by a relativelynon-compressible fluid such as water or oil; and this hydraulic fluid isretained therein so long as a normally-closed solenoid valve 41connected to electrical conductors 42 in the cable 11 is not operated toopen communication by way of a fluid passage 43 between the chamber andthe exterior of the tool 10. Accordingly, it will be appreciated thatonce the upper end of the chamber 25 has been filled with a sufficientvolume of the hydraulic fluid to shift the actuating piston 38downwardly to its illustrated position, the depending rod 39 will bepositioned in the recess 36 between the opposed enlarged heads 35 formaintaining the weighted body 33 releasably suspended just above thedisplacement piston 31.

As seen in FIGS. 2A ans 3, in the preferred manner of arranging theselectively-operable coupling means 20, the lower end of the upper body17 is adapted to be complementally received within the upper end of theenlarged longitudinal bore 28 in the lower body 19. An inwardly-openingcircumferential groove 44 is formed around the wall of the lower body 19for defining a fixed downwardly-facing inclined abutment, as at 45,adapted for engagement with generallycomplemental oppositely-directedabutment surfaces, as at 46, on outwardly-enlarged heads 47 and 48respectively arranged on the lower ends of a pair of inwardly-movablelatch fingers 49 and 50 which are in turn dependently mounted fromopposite sides of the lower end of the upper body 17. Atransverselyoriented latch member 51 is pivotally coupled, as at 52, tothe enlarged head47 of one of the fingers 49 and suitably dimensioned toengage the tip 53 of the latch member with the rear of the oppositeenlarged head 48 so as to retain the enlarged heads within thecircumferential groove 44 until the latch member is pivoted upwardly asufficient distance to bring its tip into registration with an opening54 in the opposite head. To selectively release the latch member 51 fromits depicted horizontal or transverse position, an upstanding member 55is mounted thereon and extended upwardly at a slight angle from thevertical into the lower end of the upper tool body 17. For reasons thatwill subsequently be explained in greater detail, the upper end of theupstanding member 55 is tapered, as at 56, for engagement with thecomplementally-shaped interior surface 57 ofa depending skirt 58 on thelower end of the pis ton member 31 when the displacement piston iscarried to the lower end of the fluid chamber 30 and contacts theupstanding actuating member. The purposes of this cooperativearrangement will be better appreciated once the operation of the new andimproved tool 10 is fully explained.

To initially retain the fluent substance 24 within the fluid chamber 30,the lower end of the longitudinal bore 28 is normally closed as shown inFIG. 2B by an annular valve member 59 that is slidably arranged andfluidly sealed, as at 60, within the lower end of the enlarged bore. Tonormally secure the valve member 59 in its depicted elevated position, ashear pin 61 is arranged to releasably secure the valve member to thelower body 19 until the fluid pressure of the fluent substance 24 hasbeen increased sufficiently to break the shear pin and shift the valvemember downwardly.

For reasons that will subsequently become apparent, an elongated tubularmember 62 is coaxially supported as shown in FIGS. 2A and 28 within thebore 28 in the lower body 19 and terminated at its upper end by one ormore lateral outlets 63 to provide communication between the upper endof the tubular member and the exterior of the tool 10. By providing anenlargeddiameter portion 64 on the tubular member 62 immediatelyadjacent to the normal elevated position of the valve member 59 andarranging a sealing member 65 thereon for engagement within the axialbore of the annular valve member, the fluent substance 24 thereabovecannot be displaced from the fluid chamber 30 until the valve member hasmoved downwardly a sufficient distance to bring its upper end below thesealing member 65.

The intermediate portion of the lower body 19 is sized to accommodate apair of longitudinally-spaced slidable collars 66 and 67 which arerespectively fluidly sealed, as at 68 and 69, around the body andsecured within the opposite ends of the tubular bag 18 which ispreferably formed of a suitable wear-resistant, flexible andfluid-impervious material, such as a Dacron cloth impregnated withNeoprene, that does not readily stretch. The bag 18 is formed with anexpanded diameter corresponding generally to that of the well casing 14,and is preferably foldedand lightly tied around the body 19 in thiscollapsed position. In its initiallycollapsed position illustrated inFIG. 2B, the tubular bag 18 is drawn to its full length with theslidable collars 66 and 67 at their most-widely separated positionsalong the lower body 19; and the upper collar is releasably secured inits initial position by one or more upright latch fingers 70 which areinwardly biased to retain enlarged heads 71 thereon in a circumferentialgroove 72 around the body.

It will be noted that by virtue of the sealing members 68 and 69 on theslidable collars 66 and 67, the interior of the bag 18 defines anannular fluid-tight space around the body 19. Accordingly, to providecommunication withinthe collapsed bag 13, one or more lateral ports 73are arranged in the reduced-diameter portion of the body 19 at alocation between the depicted elevated position of the upper collar 66and the lower position to which the collar will slide downwardly inresponse to cable tension after the bag is initially expanded. The lowerend of the elongated tubular member 62 is extended below the ports 73and sealingly engaged, as at 74, within the longitudinal bore 75 throughthe reduced portion of the body 19. Thus, so long as the upper collar 66is retained in its initial elevated position by the latch fingers 70,once the valve member 59 is shifted downwardly, the fluent substance 24released from the fluid chamber 30 will be directed through the annularspace between the body 19 and the lower portion of the tubular member 62and discharged into the bag 18 by way of the lateral ports 73.

It will, of course, be appreciated that once the upper collar 66 hasbeen carried downwardly (as will subsequently be described) a sufficientdistance to position the sealing member 68 on the collar below thelateral ports 73, the fluent substance 24 confined in the interior spacewithin the expanded bag 18 will be trapped therein. For reasons thatwill subsequently be explained, a second circumferential groove 76 isformed around the reduced-diameter portion of the body 19 just below thelateral ports 73 so that, once the collar 66 has shifted downwardly inrelation to the ports, the enlarged heads 71 on the latch fingers 70will engage this lower groove to prevent the upper collar fromsubsequently moving upwardly from its lower position.

The selectively-operable biasing means 21 are preferably arranged on thelower body 19 somewhat below the lower collar 67. As illustrated inFIGS. 23 and 2C,

the biasing means 21 include an annular member 77 which is slidablymounted around the reduced portion of the body 19 and adapted to bemoved upwardly thereon by a stout compression spring 78 arranged betweena body shoulder 79 and the slidable member. For reasons that willsubsequently be explained, the spring 78 is initially retained incompression by one or more ball members 86 that are respectivelyarranged in lateral recesses 81 spaced around the annular member 77 andsized for partial reception in a circumferential groove 82 formed aroundthe intermediate portion of the lower body 19. A sleeve member 83 iscoaxially mounted around the annular member 77 and has its lower portionformed with an internal diameter appropriately sized in relation to thediameter of the walls and the depth of the circumferential groove 82 toprevent outward lateral movement of the balls from the groove so long asthe ball-retainer sleeve remains in the elevated position illustratedinFIG. 2B.

To permit selective outward movement of the balls 80 from thecircumferential groove 82, longitudinal slots 84 are arranged around theupper portion of the retainer sleeve 83. Thus, upon downward movement ofthe retainer sleeve 83 in relation to the annular member 77 to bring theslots 84 into registration with the several balls 80, theupwardly-directed force of the compression spring 78 will be effectivefor shifting the annular member upwardly in relation to the lower body19 once the balls are shifted outwardly from the circumferential groove82 and into the enlarged space provided by the elongated slots. In thismanner, once the ball-retainer sleeve 83 is moved downwardly against therestraint of a relatively-weak compression spring 85 mounted between theretainer sleeve and around the annular member 77, the stout compressionspring 78 will be freed for shifting the annular member upwardly againstthe lower collar 67. To provide for the actuation of the ball-retainersleeve 83, the lower collar 67 is appropriately formed, as at 36, toengage an inwardly-turned lip 87 on the upper end of the ballretainersleeve to shift it downwardly in relation to the annular member 77 forreleasing the balls 80 from the circumferential body groove 82.

As previously mentioned, the normally-open bypass passage 23 is providedfor reducing, if not altogether equalizing, pressure differentialsexisting across the expanded bag 18 as the fluent substance 24 thereinis hardening. Accordingly, as shown in FIG. 2C, one or more lateralports 88 are formed in the lower tool body 19 well below the depictedinitial position of the lower collar 67. In this manner, the bypasspassage 23 through the body 19 between the upper and lower ports 63 and88 is defined by the tubular member 62 and the intermediate portion ofthe longitudinal bore 75 below the lower end of the tubular member. Toselectively close this bypass passage 23, the bypass control means 22include a tubular valve member 89 which is operatively disposed withinthe longitudinal bore 75 for movement upwardly from an initial positionimmediately below the lateral ports 88 to a final elevated position (asdefined by a downwardly-facing shoulder 90 in the longitudinal bore)where longitudinally-spaced sealing members 91 and 92 on the valvemember are spanning the ports and sealingly engaged with the body 19above and below the ports. Thus, the bypass control means 22 initiallyprovide fluid communication through the tubular member 62 and the bypassports 63 and 88 for accommodating well bore fluids moving past thewell-completion tool 10 during the time that the fluent substance 24 ishardening within the expanded bag 18.

To close the valve member 89, an elongated tension spring 93 is anchoredat its upper end by a transverse rod 94 (FIG. 28) to the body 19 and hasits remaining portion extended downwardly through the longitudinal bore75 (FIG. 2C). The spring 93 is terminated by a long straight portion 95which is passed through the valve member 89 and releasably secured in aninitiallystretched condition by a hook 96 coupled to a cord 97 that isreleasably secured to a geared timer mechanism 98 enclosed in anenlarged oil-filled chamber 99 in the lowermost portion of the lowertool body 19. The rotational speed of the uppermost gear 100 in thetimer mechanism 98 is regulated by a train of gears that is terminatedby a paddle-like wheel 101 which is driven by the force of the spring 93acting through the gear train. Thus, by releasably coupling the cord 97to the shaft 102 carrying the upper gear 100 of the gear train andwinding the cord therearound, the tension force of the spring 93 will beeffective for slowly rotating this uppermost gear at a speed which, byvirtue of the gear train, is regulated by the faster, but retarded,rotational speed of the rotating paddle member 101 in the oilfilledchamber 99.

Accordingly, once the cord 97 is wound around the shaft 102 and coupledto the hook 96 on the lower end of the spring 93, a preselected timeinterval will be provided before a transverse member, such as a washer103, loosely mounted on the straight portion 95 of the spring is movedupwardly to shift the valve member 89 upwardly to close the ports 88. Inother words, once the cord 97 is connected, the tension force of thespring 93 will begin slowly unwinding the cord from the shaft 102 sothat, once the gear 100 has been rotated a sufficient number ofrevolutions to substantially unwrap the cord, the lower end of the cordwill be released from the shaft and the spring will then contract tojerk the washer 103 upwardly for carrying the valve member 89 to itsfinal port-closing position.

To prepare the new and improved well-completion tool 10 for operation,the fluid chamber above the weight-releasing piston 38 is filled with asufficient volume of a hydraulic fluid to shift the piston against thespring 40 to a position where the depending rod 39 extends downwardlyinto the recess 36. The weighted body 33 is forced upwardly, compressinga coil spring 104 thereabove until the enlarged heads 35 of the latchfingers 34 are on opposite sides of the rod 39 and are supported on theshoulder 37 for retaining the weighted body 33 in its elevated positionabove the fluid-displacement piston 31. The lower end of the upper body17 is complementally fitted into the upper end of the lower body 19 andthe latch member 51 is properly positioned to retain the opposedenlarged heads 47 and 48 in the internal circumferential groove 44. Theupper valve member 59 is secured in its upper or closed poisition by theshear pin 61; and the enclosed fluid chamber is then filled with asuitable plastic or cementitious initially-fluent substance, as at 24,which will harden into a solid mass that preferably expands slightly asit fully hardens.

The annular member 77 is shifted into position on the intermediateportion of the tool body 19 so as to place the balls 80 in the groove 82and releasably retain the compression spring 78 in a compressedcondition. The tension spring 93 is extended and connected by the hook96 to the release cord 97 which has been wrapped around the gear shaft102. As previously mentioned, the delay provided by the timer mechanism98 before the bypass passage 23 is closed is governed by the number ofturns or wraps of the cord 97 around the shaft 102. This time intervalis, of course, selected so that the valve member 89 will not be actuateduntil some time later which is calculated to be sufficient to permit theinitially-fluent substance 24 to have at least substantially hardened.

The tool 10 is then lowered into the well bore 13 by means of thesuspension cable 11. Once the wellcompletion tool 10 has emerged fromthe lower end of the tubing string 12 and has reached a selectedposition therebelow, an electrical signal is sent through the cableconductors 42 to actuate the solenoid valve 41. As previously explained,once the solenoid valve 41 is opened, the hydraulic fluid within theupper chamber 25 will be discharged through the now-opened passage 43 asthe compression spring 40 shifts the weightreleasing piston 38 upwardly.Once the weightreleasing piston 38 has reached a sufficiently-elevatedposition to withdraw the depending rod 39 from between the opposed ends35 of the latch fingers 34, the weighted body 33 will be released.

Once the weighted body 33 is released, the force of the compressedspring 104 is effective for accelerating the weighted body rapidlydownwardly so that it strikes the fluid-displacement piston 31 withconsiderable impact. In this manner, a substantial shock or pressurewave is developed in the fluent substance 24 which is effective forshifting the annular valve member 59 downwardly with sufficient force tobreak the shear pin 61. Once the shear pin 61 has failed, the uppervalve member 59 will be moved downwardly a sufficient distance to bringits upper end below the seal 65 on the enlarged-diameter portion 64 ofthe axial tubular member 62 to open communication between the fluidchamber 30 and the filling ports 73 by way of the annular space betweenthe axial tubular member and the inner wall of the intermediate portionof the lower body 19. A sealing member 105 is arranged on the lower endof the valve member 59 for sealing engagement with the lowermost portionof the enlarged bore 28 to prevent loss of the fluent substance 24through a pressureequalizing port 106 provided in the enlarged borebelow the upper sealing member 60.

Once the weighted body 33 has come to rest on top of thefluid-displacement piston 31, the weight of this body will be effectivefor moving the piston on downwardly through the fluid chamber 30 toforcibly displace a portion, as at 107, of the fluent substance 24through the filling ports 73 and into the expansible bag 18. It will, ofcourse, be appreciated that since the fluent substance 24 is initiallyat the hydrostatic pressure of the well bore fluids, the pressuredeveloped by the weighted body 33 will be in addition to the hydrostaticpressure. Thus, as the bag 18 is filling, the increased fluid pressuredeveloped in the fluent substance 24 by the weighted body 33 acting onthe displacement piston 31 will be effective for expanding the bagoutwardly with the enclosed portion 107 of the material and into contactwith the walls of the well casing 14 immediately adjacent thereto.Expansion of the tubular bag 18 will, of course, be effective fordrawing the unrestrained lower slidable collar 67 upwardly along theintermediate portion of the body 19 toward the still-latched uppercollar 66. lt should be noted that the latch fingers 70 are stiff enoughthat the expansion of the bag 18 will draw the lower collar 67 upwardlywithout releasing the enlarged heads 71 from the upper circumferentialgroove 72.

Accordingly, when the expansible bag 18 is fully expanded, it willinitially be in a position in which its opposite ends substantiallyassume a generallyhemispherical configuration instead of the toroidalconfiguration shown in FIG. 4. At this point, there will still be asubstantial volume of the still-fluent substance 24 remaining in thefluid chamber 31} so that the increased fluid pressure developed in theinterior of the bag 18 by the weight of the body 33 acting on the piston31 will expand the bag outwardly against the well casing 14 with amoderate lateral force. Once the bag 18 is fully expanded, the dischargeflow of the fluent substance 24 from the fluid chamber 30 will, ofcourse, temporarily cease and the displacement piston 31 and theweighted body 33 will come to rest at the upper fluid level of thefluent substance still remaining in the fluid chamber.

It will be recognized that the fluid pressure expanding the bag 18outwardly will urge the exterior of the bag against the well casing 14with a lateral force that is effective to frictionally secure the bagagainst longitudinal movement. Therefore, upon upward movement of thesuspension cable 11, the upper body 17 and the lower body 19 willinitially be moved upwardly in relation to the stationary expanded bag18 and the upper and lower slidable collars 66 and 67. As willsubsequently be explained in detail, this upward movement is effectivefor consecutively blocking further communication to the interior spacein the expanded bag 18, actuating the biasing means 21, and ultimatelyfreeing the upper tool body 17 from the lower tool body 19.

First of all, upon upward movement of the lower body 19, theinwardly-enlarged ends 71 of the latch fingers 74) will be cammedoutwardly by the lower surface of the upper circumferential groove 72 torelease the upper collar 66 for sliding movement in relation to the toolbody. Thus, the continued upward movement of the lower body 19 will beeffective for carrying the fill ports 73 above the stationary uppercollar 66 and then bringing the lower circumferential groove 76immediately below the fill ports up to or, perhaps, slightly above theheads 71 of the latch fingers 711. It will, of course, be recognizedthat once the lateral ports 73 pass above the fluid seal 68 on the uppercollar 66, that portion 107 of the fluent substance 24 which has filledthe expanded bag 18 will be sealingly enclosed therein. Moreover, oncethe lower circumferential groove 76 engages or passes above the latchfingers 70, the upper collar 66 cannot return upwardly in relation tothe body 19 to a position where the ports 73 are again in communicationwith the interior space within the bag 18. Furthermore, as the lowerbody 19 is moved upwardly, the releasably-coupled annular member 77 willbe carried upwardly toward the stationary lower collar 67 so as to bringthe depending portion 86 thereof into contact with the inwardly-directedlip 87 of the ballretainer sleeve 83. Then, as the lower body 19 ismoved further upwardly, the ball-retainer sleeve 83 will be halted andthe continued movement of the annular member 77 will carry the balls 80upwardly into registration with the elongated slots 84. As previouslydescribed, once the balls 80 move into registration with the elongatedslots 84, they will be free to move outwardly into the enlarged spacetherearound to disengage the balls from the circumferential groove 82around the intermediate portion of the body 19.

Accordingly, once the balls 80 are disengaged from the circumferentialgroove 82, the compressed biasing spring 78 will be released forforcibly urging the annular member 77 upwardly against the lower collar67. Thus, as best seen in FIG. 4, once the compression spring 78 isreleased, it will impose a substantial upwardly-directed axial forceagainst the lower end of the stationary expanded bag 18. The axial forcewill be effective for further increasing the fluid pressure of thestill-fluent substance 107 trapped within the bag 18 which (if theenlarged heads 71 are below the groove 76) will initially move the uppercollar 66 upwardly to accommodate the corresponding depression of thelower end of the bag. Once, however, the upper collar 66 reaches aposition on the intermediate portion of the body 19 where the latchfingers are adjacent to the circumferential groove 76 just below thefilling ports 73, the enlarged ends 71 thereof will be urged into thecircumferential groove 76 to secure the upper collar from further upwardmovement. Once the upper collar 66 is secured against further movementin relation to the elongated body 19, the upwardly-directed axial forceimposed on the lower end of the bag 18 by the stout compression spring78 will be effective for developing a downwardly-directed opposing oraxial reaction force on the upper end of the expanded bag for depressingthe central portions of the upper and lower ends of the bag inwardly sothat, ultimately, the expanded bag will assume the generally-toroidalconfiguration depicted in FIG. 4. The significance of this toroidalconfiguration is fully expained in US. Pat. No. 3,578,083 and,therefore, needs no further explanation.

Once the filling ports 73 are uncovered, the weighted body 33 willresume downward movement of the piston 31 to displace the remainder ofthe fluent substance 24 contained within the fluid chamber 30 into thewell bore annulus defined between the casing 14 and that portion of theelongated body 19 projecting upwardly above the expanded bag 18. In thismanner, the remainder of the fluent substance 24 will be deposited ontop of the expanded bag 18, as at 108, to further assure that animpermeable plug or barrier of substantial vertical height will beformed in the well bore 13 once the two portions of the fluentsubstance, as at 107 and 168, have ultimately expanded and hardened.

As best seen in FIG. 3, as the piston 31 nears the end of its travel inthe fluid chamber 30 (as defined by one or more inwardly-projectingstops 109 in the longitudinal bore 27), the lower edge of the pistonskirt 58 will pass over the tapered end 56 of the upstanding member 55.It is, of course, readily apparent that the cooperative arrangement ofthe complemental surfaces 56 and 57 will quickly tilt the upstandingmember 55 toward a more-erect position which correspondingly pivots thelatch member 51 upwardly from its depicted latching position forbringing the nose 53 of the latch member into registration with the hole54 in the head 48. lnward movement of the opposed heads 47 and 48 will,of

course, secure the latch member 51 in its tool-releasing position as thelatch tip 53 enters the hole 54.

As explained in U.S. Pat. No. 3,578,083, the perimeter of the bag 18will be urged outwardly against the wall of the casing 14 with anincreased anchoring force that is proportionally related to the totalpressure of the still-fluent substance 107 confined within the expandedbag. Accordingly, as shown in FIG. 5, once the bag 18 is securelyanchored in this manner, the upper body 17 of the tool is separated fromthe lower body 19 by simply pulling further on the suspension cable 11so that the heads 47 and 48 of the latch fingers 49 and 50 will bereleased from the circumferential groove 44 at the upper end of the bodyonce the displacement piston 31 has engaged the upstanding member 55 andshifted the latch 51 above the latch head 48. Then, at somepredetermined time thereafter, the timer mechanism 98 will function torelease the tension spring 93 so as to shift the valve member 89upwardly across the lower bypass ports 88 and permanently close thebypass passage 23.

It will, of course, be appreciated that the several actions describedabove by reference to FlGS. 35 will occur successively once the solenoidvalve 41 is opened and the cable 11 is pulled upwardly to close thefilling ports 73 and reform the expanded bag 18 into its toroidalconfiguration. Thus, by simply maintaining a moderate strain on thecable 11, at the completion of the setting operation the release of thecoupling means will occur and the two bodies 17 and 19 will be separated without further action.

As previously mentioned, the new and improved coupling means 20 employedwith the completion tool 10 of the present invention are particularlyarranged to re liably retain the upper and lower tool bodies 17 and 19latched to one another even when severe shocks are imposed thereon. Onthe other hand, in keeping with the objects of the present invention, itis also essential that the coupling means 20 be fully capable ofdependable actuation to permit the upper body 17 to be easily separatedfrom the lower body 19 even when there are increased frictional forcesotherwise tending to retain the enlarged heads 47 and 48 in thecircumferential body groove 44 such as will occur under extreme tensionloads on the suspnsion cable 11.

These two conditions i.e., resistance to shock and ease of releasewould, of course, ordinarily be considered to be contrary to oneanother. Thus, heretofore, the usual technique has been to attempt toreach a compromise where a typical release mechanism will hopefullywithstand moderate shocks but still release with only a slightly-higheractuatingforce than is preferred. As is typical in most situations suchas this, neither of the opposing conditions are fully satisfied; and,often as not, a tool malfunction will occur.

Accordingly, the new and improved coupling means 20 employed with thepresent invention are cooperatively arranged to meet both conditions.First of all, to assure that the tool bodies 17 and 19 will be reliablyreleased, it is preferred to employ only the two latch finmovement ofthe latch member. Thus, only a very slight downward force is required ofthe displacement piston 31 to assure the release of the bodies 17 and19.

As mentioned above, two frictional forces are involved in determiningthe ease with which the bodies 17 and 19 can be separated. First of all,the relative inclination of the abutment surfaces 45 and 46 will governthe tension force which must be imposed on the cable 11 to operate thecoupling means 20. For instance, if the abutment surfaces 45 and 46 areperpendicular with respect to the longitudinal axis of the tool gers 49and 50 to couple the bodies together. In this 10, all of the tensionforces on the cable 11 would be directly applied to the abutmentsurfaces 45 and 46 along a longitudinal load axis and there would be nolaterally-directed force tending to move the latch fingers 49 and 50inwardly so as to release the bodies 17 and 19. Thus, the angle ofinclination of the opposed abutment surfaces 45 and 46 must be selectedso as to at least produce an inwardly-directed lateral force on thelatch fingers 49 and 50 in response to tension on the cable 11.

The other frictional force which will determine how readily the couplingmeans 20 will operate to release the bodies 17 and 19 is the frictionalforce imposed between the rear surface of the latch finger 48 and thenose 53 of the latch member 51. It will, of course, be appreciated thatthis frictional force will be dependent upon the inclination of theabutment surfaces 45 and 46 since the resultant inwardly-directedlateral force acting on the nose 53 of the latch member 51 will bedirectly dependent on the angle of this inclination. Thus, as this angleincreases, the frictional force tending to prevent upward pivotalmovement of the latch member 51 will corerspondingly increase.

As a result, therefore, the angle of inclination of the abutmentsurfaces 45 and 46 is selected to assure inward movement of the latchfingers 48 and 49 with a moderate cable tension but without imposing anextreme inwardly-directed lateral force on the latch member 51. Althoughthere are, of course, many variables, it has been found that this angleof inclination a ll lll lfilll fifllfi tens o @P t from the horizontal,with 30 being the particular choice used in the preferred embodiment ofthe present invention. This choice is, however, not to be considered asa limitation on the scope of the present invention.

It would seem that by virtue of the ease with which the latch member 51can be pivoted upwardly, the coupling means 20 would be highly sensitiveto even moderate shock forces which would tend to inadvertently releasethe two bodies 17 and 19. However, the coupling means 20 arecooperatively arranged to withstand substantial impacts and shocks. Forinstance, downward movement of the fluent substance 24 past the latchmember 51 is totally incapable of releasing the latch member since thecontact of the upper portion of the upstanding member 55 against theadjacent wall of the lower body 19 prevents downward pivotal movement ofthe latch member. Similarly, any downwardlyacting pressure surges (suchas when the weighted body 33 is released) on the latch member 51 areincapable of tripping the latch member. The same protection is alsoprovided even when the tool 10 strikes a projection as it is beinglowered into the well bore 13 and is slowed or rapidly halted so as toimpose downwardlyimposed inertial forces on the latch member 51.

Those skilled in the art will, of course, appreciate that should a sharplateral force or shock be imposed on the right-hand side (as viewed inthe drawings) of the lower tool body 19 or the tool be swung so as toimpact its right-hand side against an object, the sensitively-arrangedlatch member 51 could possibly be pivoted upwardly by inertia. However,to counter this reaction, the mid-portion of the upstanding member 55 issubstantially reduced, as at H10, for greatly minimizing the mass whichwould otherwise tend to pivot the latch member 51 upwardly (in aclockwise direction as viewed in FIG. 3) in response to these forces.Impacts or shocks acting in the reverse manner will, of course, simplytend to pivot the latch member 51 in the opposite direction and thiswill be prevented by the upstanding member 55 resting on the body 19. Tofurther counter this unwanted reaction, a spring 111 is mounted on thelatch member 51 adjacent to the pivot 52 so as to provide acounteracting biasing force about equal to the inertial force of theupstanding member 55. Thus, a lateral inertial force tending to shiftthe upstanding member 55 upwardly toward a more-erect position isopposed by the biasing action of the spring 111 urging the latch member51 downwardly.

Accordingly, it will be appreciated that the new and improved completiontool 10 of the present invention is particularly arranged to reliablyplug a well bore with a hardenable substance carried in the tool. Byarranging the tool with upper and lower bodies which are releasablysecured together by shock-resistant release means which are releasedonly by the discharge of the fluent substance onto an extendible supporton the lower body, the upper body can be easily separated from the lowerbody. Moreover, by virtue of the unique design of the shock-resistantrelease means, the risk that the tool bodies will be inadvertentlyuncoupled is substantially reduced without-impairing the sensitivity ofthe release means.

While only a particular embodiment of the present invention has beenshown and described, it is apparent that changes and modifications maybe made without departing from this invention in its broader aspects;and, therefore, the aim in the appended claims is to cover all suchchanges and modifications as fall within the true spirit and scope ofthis invention.

What is claimed is:

1. Apparatus adapted for plugging a well bore an comprising:

an upper body adapted to be suspended in a well bore;

a lower body tandemly arranged in relation to said upper body;

means defining an enclosed chamber in at least one of said bodiesadapted to contain an initially-fluent hardenable substance;

means cooperatively arranged on said lower body and including extendiblesupport means adapted for extension outwardly from said lower body forcarrying a fluent substance discharged from said enclosed chamber;

means cooperatively arranged for discharging a fluent substance fromsaid enclosed chamber onto said support means and including a pistonselectively movable within said enclosed chamber from an elevatedposition to a lower position; and means releasably intercoupling saidbodies and including means on one of said bodies defining a firstabutment surface, means on the other of said bodies and including amovable member having an opposing second abutment surface cooperativelyarranged for lateral movement between a first position where saidabutment surfaces are abutted in longitudinal alignment with one anotherfor coupling said bodies together and a second position where saidabutment surfaces are laterally separated for uncoupling said bodies, alatch member pivotally coupled to one of said bodies and adapted forpivotal movement longitudinally between a transversely-extended latchingposition for retaining said movable member from movement away from itssaid first position and a longitudinallydisplaced releasing position forfreeing said movable member for movement to its said second position,and latch-actuating means cooperatively arranged between said latchmember and said piston and adapted for pivoting .said latch member toits said releasing position only upon movement of said piston toward itssaid lower position.

2. The apparatus of claim 1 wherein said latchactuating means includemeans cooperatively arranged on said latch member for counteractinglaterallydirected forces acting thereon-and tending to pivot said latchmember toward its said releasing position before said piston has movedtoward its said lower position.

3. The apparatus of claim 1 wherein said latchactuating means includefirst and second actuating members respectively mounted on said pistonand said latch member and cooperatively arranged to be coengaged as saidpiston nears its said lower position, and first and second means on saidfirst and second actuating members respectively and responsive upontheir coengagement for pivoting said latch member toward its saidreleasing position as said piston reaches its said lower position.

4. The apparatus of claim 3 further including:

balancing means cooperatively arranged on said latch member forcounteracting laterally-directed inertial forces acting in one directionon said sec ond actuating member and tending to pivot said latch membertoward its said releasing position be fore said piston is moved towardits said lower position.

5. Apparatus adapted for plugging a well bore and comprising:

an upper body adapted for suspension in a well bore and having anenclosed chamber defined therein adapted to contain an initiallyfluenthardenable substance;

at lower body having its upper end adapted to be interfitted with thelower end of said upper body; means cooperatively arranged on said lowerbody and including extendible support means adapted to be extendedoutwardly from said lower body for carrying a fluent substancedischarged from said enclosed chamber;

means cooperatively arranged for discharging a fluent substance fromsaid enclosed chamber onto said support means and including a pistonselectively movable within said enclosed chamber from an elevatedposition to a lower position;

means releasably intercoupling said bodies and including first andsecond longitudinally-disposed locking fingers coupled to the oppositesides of the interfitted end of one of said bodies and adapted forlateral movement between outwardly-extended and inwardly-contractedpositions, means on said locking fingers defining outwardly-directedfirst abutment surfaces facing said interfitted end of said one body,means on the opposite sides of the interfitted end of the other of saidbodies defining inwardly-directed second abutment surfaces facing saidinterfitted end of said other body and adapted to be abutted with saidfirst abutment surfaces to prevent separation of said bodies only solong as said locking fingers are retained in their saidoutwardly-extending position, a latch member having a length selected tospan the lateral distance separating said locking fingers, and meanspivotally coupling one end of said latch member to said first lockingfinger for pivotal movement along a generally-longitudinal plane betweena fingerlatching position where the other end of said latch member isadjacent to said second locking finger to retain said locking fingers intheir said outwardlyextending positions and a finger-releasing positionwhere said other end of said latch member is laterally displaced fromsaid second locking finger to free said locking fingers for movement totheir said inwardly-contracted positions; and

means adapted for selectively moving said latch member from its saidfinger-latching position to its said finger-releasing position andincluding first and second cam surfaces cooperatively arranged on saidlatch member and said piston respectively for pivoting said latch memberto its fingerreleasing position upon movement of said piston toward itssaid lower position sufficient to coengage said first and second camsurfaces.

6. The apparatus of claim 5 wherein said locking fingers are on saidupper body.

7. The apparatus of claim 5 wherein said fingerreleasing position ofsaid latch member is above its said finger-latching position.

8. The apparatus of claim 5 wherein said locking fingers are on saidupper body and said finger-releasing position of said latch member isabove its said fingerlatching position; and further including;

an opening cooperatively arranged in said second locking finger forreceiving said other end of said latch member upon pivotal movementthereof to its said finger-releasing position.

9. The apparatus of claim 5 wherein said first and second abutmentsurfaces are respectively inclined in relation to the longitudinal axesof said bodies.

10. The apparatus of claim 9 wherein the angle of inclination of saidabutment surfaces is between about 30 and about 75 from saidlongitudinal axes.

11. Apparatus adapted for plugging a well bore and comprising:

upper and lower tandemly-interfitted bodies adapted for suspension in awell bore and having an enclosed chamber defined in at least said upperbody for containing an initially-fluent hardenable substance; anexpansible tubular bag mounted around said lower body and adapted forexpansion into anchoring engagement with a well bore wall upon receivinga supply of a fluent substance discharged from said enclosed chamber;means cooperatively arranged for discharging a fluent substance intosaid expansible bag from said enclosed chamber and including a pistonselectively movable therein from an elevated position to a lowerposition;

means releasably intercoupling the adjacent ends of said interfittedbodies and including a pair of laterally-flexible locking fingersdependently mounted on opposite sides of said upper body and extendinginto said lower body, means on said locking fingers respectivelydefining upwardly-facing outwardly-projecting first inclined shoulders,means on the interior of said lower body defining downwardly-facinginwardly-opening second inclined shoulders adapted to be coengaged bysaid first shoulders only so long as said locking fingers are retainedagainst inwardly-directed lateral movement from a body-locking positionwhere said first and second shoulders are co-engaged to a body-releasingposition where said first shoulders are laterally separated from saidsecond shoulders, a latch member having a length selected tosubstantially span the lateral distance separating opposedinwardly-facing surfaces on said locking fingers, and means pivotallycoupling one end of said latch member to one of opposed surfaces forpivotal movement along a generally-longitudinal plane between afinger-latching position where the other end of said latch member ismovably engaged with the other of said opposed surfaces and afingerreleasing position where said other latch end is longitudinallydisplaced from said other opposed surface sufficiently to free saidlocking fingers for inward movement to their said'body-releasingposition; and

actuating means adapted for pivoting said latch member from its saidfinger-latching position to its said finger-releasing position inresponse to the discharge of a fluent substance from said enclosedchamber into said expansible bag.

12. The apparatus of claim 11 wherein said actuating means include:

a first cam member dependently mounted on said piston and including adownwardly-facing inclined cam surface, and a second cam member mountedin an upright position on said latch member and including anupwardly-facing inclined cam surface adapted to be contacted by saidfirst cam surface as said piston approaches.

13. The apparatus of claim 12 further including means on said second cammember cooperatively arranged for minimizing inertial forces acting onsaid second cam member and tending to pivot said latch member to itssaid finger-releasing position.

14. The apparatus of claim 11 wherein said fingerreleasing position ofsaid latch member is above its said finger-latching position; andfurther including:

means on said other opposed surface defining an opening adapted toreceive said other end of said latch member whenever said latch memberis pivoted to its said finger-releasing position.

15. The apparatus of claim 14 wherein said actuating means include:

a first actuating member mounted in a generallyupright position on saidlatch member and cooperatively arranged to engage the upper portion ofsaid first actuating member with said other opposed surface above saidopening when said latch member is in its said finger-latching positionso that downwardly-directed inertial forces acting on said latch memberwill not pivot said latch member downwardly from its said fingerlatching position; a second actuating member dependently coupled to saidpiston and adapted to engage said first actuating member as said pistonapproaches its said lower position; an upwardly-facing camming surfaceon said upper portion of said first actuating member inclined upwardlyand away from the point of engagement of said upper portion with saidother opposed surface; and a downwardly-facing inclined camming surfaceon said second actuating member substantially complemental to saidupwardly-facing camming surface and cooperatively arranged forprogressively tilting said first actuating member away from said otheropposed surface as said piston approaches its said lower position topivot said latch member from its said finger-latching position to itssaid fingerreleasing position.

16. The apparatus of claim 15 further including:

means cooperatively arranged on said first'actuating member forminimizing inertial forces acting thereon and tending to pivot saidlatch member upwardly to its said finger-releasing position.

17. The apparatus of claim 15 further including:

means cooperatively arranged on said first actuating member forminimizing inertial forces acting thereon and tending to pivot saidlatch member upwardly to its said finger-releasing position; and

spring means normally biasing said latch member downwardly toward itssaid finger-latching positlon.

1. Apparatus adapted for plugging a well bore and comprising: an upperbody adapted to be suspended in a well bore; a lower body tandemlyarranged in relation to said upper body; means defining an enclosedchamber in at least one of said bodies adapted to contain aninitially-fluent hardenable substance; means cooperatively arranged onsaid lower body and including extendible support means adapted forextension outwardly from said lower body for carrying a fluent substancedischarged from said enclosed chamber; means cooperatively arranged fordischarging a fluent substance from said enclosed chamber onto saidsupport means and including a piston selectively movable within saidenclosed chamber from an elevated position to a lower position; andmeans releasably intercoupling said bodies and including means on one ofsaid bodies defining a first abutment surface, means on the other ofsaid bodies and including a movable member having an opposing secondabutment surface cooperatively arranged for lateral movement between afirst position where said abutment surfaces are abutted in longitudinalalignment with one another for coupling said bodies together and asecond position where said abutment surfaces are laterally separated foruncoupling said bodies, a latch member pivotally coupled to one of saidbodies and adapted for pivotal movement longitudinally between atransversely-extended latching position for retaining said movablemember from movement away from its said first position and alongitudinally-displaced releasing position for freeing said movablemember for movement to its said second position, and latch-actuatingmeans cooperatively arranged between said latch member and said pistonand adapted for pivoting said latch member to its said releasingposition only upon movement of said piston toward its said lowerposition.
 2. The apparatus of claim 1 wherein said latch-actuating meansinclude means cooperatively arranged on said latch member forcounteracting laterally-directed forces acting thereon and tending topivot said latch member toward its said rEleasing position before saidpiston has moved toward its said lower position.
 3. The apparatus ofclaim 1 wherein said latch-actuating means include first and secondactuating members respectively mounted on said piston and said latchmember and cooperatively arranged to be coengaged as said piston nearsits said lower position, and first and second means on said first andsecond actuating members respectively and responsive upon theircoengagement for pivoting said latch member toward its said releasingposition as said piston reaches its said lower position.
 4. Theapparatus of claim 3 further including: balancing means cooperativelyarranged on said latch member for counteracting laterally-directedinertial forces acting in one direction on said second actuating memberand tending to pivot said latch member toward its said releasingposition before said piston is moved toward its said lower position. 5.Apparatus adapted for plugging a well bore and comprising: an upper bodyadapted for suspension in a well bore and having an enclosed chamberdefined therein adapted to contain an initially-fluent hardenablesubstance; a lower body having its upper end adapted to be interfittedwith the lower end of said upper body; means cooperatively arranged onsaid lower body and including extendible support means adapted to beextended outwardly from said lower body for carrying a fluent substancedischarged from said enclosed chamber; means cooperatively arranged fordischarging a fluent substance from said enclosed chamber onto saidsupport means and including a piston selectively movable within saidenclosed chamber from an elevated position to a lower position; meansreleasably intercoupling said bodies and including first and secondlongitudinally-disposed locking fingers coupled to the opposite sides ofthe interfitted end of one of said bodies and adapted for lateralmovement between outwardly-extended and inwardly-contracted positions,means on said locking fingers defining outwardly-directed first abutmentsurfaces facing said interfitted end of said one body, means on theopposite sides of the interfitted end of the other of said bodiesdefining inwardly-directed second abutment surfaces facing saidinterfitted end of said other body and adapted to be abutted with saidfirst abutment surfaces to prevent separation of said bodies only solong as said locking fingers are retained in their saidoutwardly-extending position, a latch member having a length selected tospan the lateral distance separating said locking fingers, and meanspivotally coupling one end of said latch member to said first lockingfinger for pivotal movement along a generally-longitudinal plane betweena finger-latching position where the other end of said latch member isadjacent to said second locking finger to retain said locking fingers intheir said outwardly-extending positions and a finger-releasing positionwhere said other end of said latch member is laterally displaced fromsaid second locking finger to free said locking fingers for movement totheir said inwardly-contracted positions; and means adapted forselectively moving said latch member from its said finger-latchingposition to its said finger-releasing position and including first andsecond cam surfaces cooperatively arranged on said latch member and saidpiston respectively for pivoting said latch member to itsfinger-releasing position upon movement of said piston toward its saidlower position sufficient to coengage said first and second camsurfaces.
 6. The apparatus of claim 5 wherein said locking fingers areon said upper body.
 7. The apparatus of claim 5 wherein saidfinger-releasing position of said latch member is above its saidfinger-latching position.
 8. The apparatus of claim 5 wherein saidlocking fingers are on said upper body and said finger-releasingposition of said latch member is above its said finger-latchingposition; and further including; an opening cooperatively arranged insaid second locking finger for receiving said other end of said latchmember upon pivotal movement thereof to its said finger-releasingposition.
 9. The apparatus of claim 5 wherein said first and secondabutment surfaces are respectively inclined in relation to thelongitudinal axes of said bodies.
 10. The apparatus of claim 9 whereinthe angle of inclination of said abutment surfaces is between about 30*and about 75* from said longitudinal axes.
 11. Apparatus adapted forplugging a well bore and comprising: upper and lowertandemly-interfitted bodies adapted for suspension in a well bore andhaving an enclosed chamber defined in at least said upper body forcontaining an initially-fluent hardenable substance; an expansibletubular bag mounted around said lower body and adapted for expansioninto anchoring engagement with a well bore wall upon receiving a supplyof a fluent substance discharged from said enclosed chamber; meanscooperatively arranged for discharging a fluent substance into saidexpansible bag from said enclosed chamber and including a pistonselectively movable therein from an elevated position to a lowerposition; means releasably intercoupling the adjacent ends of saidinterfitted bodies and including a pair of laterally-flexible lockingfingers dependently mounted on opposite sides of said upper body andextending into said lower body, means on said locking fingersrespectively defining upwardly-facing outwardly-projecting firstinclined shoulders, means on the interior of said lower body definingdownwardly-facing inwardly-opening second inclined shoulders adapted tobe coengaged by said first shoulders only so long as said lockingfingers are retained against inwardly-directed lateral movement from abody-locking position where said first and second shoulders areco-engaged to a body-releasing position where said first shoulders arelaterally separated from said second shoulders, a latch member having alength selected to substantially span the lateral distance separatingopposed inwardly-facing surfaces on said locking fingers, and meanspivotally coupling one end of said latch member to one of opposedsurfaces for pivotal movement along a generally-longitudinal planebetween a finger-latching position where the other end of said latchmember is movably engaged with the other of said opposed surfaces and afinger-releasing position where said other latch end is longitudinallydisplaced from said other opposed surface sufficiently to free saidlocking fingers for inward movement to their said body-releasingposition; and actuating means adapted for pivoting said latch memberfrom its said finger-latching position to its said finger-releasingposition in response to the discharge of a fluent substance from saidenclosed chamber into said expansible bag.
 12. The apparatus of claim 11wherein said actuating means include: a first cam member dependentlymounted on said piston and including a downwardly-facing inclined camsurface, and a second cam member mounted in an upright position on saidlatch member and including an upwardly-facing inclined cam surfaceadapted to be contacted by said first cam surface as said pistonapproaches.
 13. The apparatus of claim 12 further including means onsaid second cam member cooperatively arranged for minimizing inertialforces acting on said second cam member and tending to pivot said latchmember to its said finger-releasing position.
 14. The apparatus of claim11 wherein said finger-releasing position of said latch member is aboveits said finger-latching position; and further including: means on saidother opposed surface defining an opening adapted to receive said otherend of said latch member whenever said latch member is pivoted to itssaid finger-releasing position.
 15. The apparatus of claim 14 whereinsaid actuating means include: a first actuating member mounted in agenerally-upright positiOn on said latch member and cooperativelyarranged to engage the upper portion of said first actuating member withsaid other opposed surface above said opening when said latch member isin its said finger-latching position so that downwardly-directedinertial forces acting on said latch member will not pivot said latchmember downwardly from its said finger latching position; a secondactuating member dependently coupled to said piston and adapted toengage said first actuating member as said piston approaches its saidlower position; an upwardly-facing camming surface on said upper portionof said first actuating member inclined upwardly and away from the pointof engagement of said upper portion with said other opposed surface; anda downwardly-facing inclined camming surface on said second actuatingmember substantially complemental to said upwardly-facing cammingsurface and cooperatively arranged for progressively tilting said firstactuating member away from said other opposed surface as said pistonapproaches its said lower position to pivot said latch member from itssaid finger-latching position to its said finger-releasing position. 16.The apparatus of claim 15 further including: means cooperativelyarranged on said first actuating member for minimizing inertial forcesacting thereon and tending to pivot said latch member upwardly to itssaid finger-releasing position.
 17. The apparatus of claim 15 furtherincluding: means cooperatively arranged on said first actuating memberfor minimizing inertial forces acting thereon and tending to pivot saidlatch member upwardly to its said finger-releasing position; and springmeans normally biasing said latch member downwardly toward its saidfinger-latching position.